Open hearth furnace



June 20, 1933. E. E. McVEY 1,914,577

OPEN HEARTH FURNAGE Filed Dec. 17, 1950 Eig. j

WITNESS BYMF/ 3% 'Y TToA/ys Patented June 20, 1933 FFCE ELMER E. MCVEY, F YOUNGS'IOWN, OHIO OPEN HEARTH' FURNACE Application led December 17, 1930. Serial No. 502,911.

The useful life of an open hearth furnace is limited by the materials used in its construction, namely, the refractories of which the walls, roof, hearth and like parts are built and the metal elements employed for binding the said parts together, such as the buckstays and skew back channels. Necessarily, the cost of maintaining the refractories and metallic elements in serviceable condition by effecting suitable repairs from time to time as required and finally rebuilding the furnace as a whole when repairs are no longer possible, is a factor entering into the cost of operating the furnace and is reflected in the cost of producing each ton of steel manufactured; thus, with a view to reducing the ultimate cost of the product as fai' as possible, it is requisite that the useful life of the furnace be prolonged to the maximum extent consistent with ability to manufacture a good grade of steel, and consequently, improvements tending to enliance the life of various parts of the furnace as Well as to minimize the expense incident to repairing or replacing them are desirable in that they result in prolonging the useful life of the furnace as a whole while reducing the cost incident to maintaining it in satisfactory working condition.

The present invention, therefore, has for its primary object the construction of the furnace roof in such manner as to reduce the amount 0f material initially required therefor while affording a suliicient body or bulk to resist the action of the heating gases at those points at which it is subjected to their maximum destructive effect and .enhancing the life of the roof by preventing, 0r at least postponing, collapse of the ioof at its center when the roof structure as a whole is weakened through the erosive action of the gases adjacent the point-s of juncture of the roof and the side walls.

Thus, in accordance. with my invention, I am enabled, through the provision of the means to which I have generally referred, to prolong the loperative life of the furnace as a whole with consequent lowering of the operating cost thereof andcorresponding reduction in the cost per ton of the steel manufactured in it. l

To enable those skilled in the art to comprehend and practise my invention, I have therefore illustrated in the accompanying drawing and shall now describe a typical open hearth furnace embodying my improvements, but it should be understood, however, that the latter are equally applicable to furnace of other types than that to which I have chosen to refer.

Inthe said drawing, in which only such portions of the furnace are shown as are requisite for a proper comprehension of the invention, Fig. l is a fragmentary elevation of the front or charging side of the furnace partially broken away into central vertical section; Fig. 2 is a transverse section through the furnace on the line 2-2 in Fig. l. Throughout the drawing the same characters of reference are used to designate the same parts.

As shown, the furnace comprises the usual heart l, front wall 2, rear wall 3 and roof s, the front wall being provided with charging' doors or openings 5-5 set at longitudinally spaced intervals. For supporting the front and back walls the usual front buckstays 6 and rear buckstays 7 are provided; these buckstays consist of steel beams desirably arranged in groups of three at suitable longitudinally separated intervals, the beams of each group being spaced a comparatively short dist-ance apart. Near their lower ends the buckstays may be tied .together by longitudinally extending stringers 8 and near their upper ends by other stringers or channels 9 in turn tied together transversely of the furnace by long bolts 10 and also by cross tie beams ll. Beneath the groups of buckstays cast iron supports 13 may be disposed upon which are located plates 14 level with the charging floor (not shown) while the door openings are provided with vertically slidable closures (not shown) which may be of any suitable construction. It will thus be apparent that the furnace is in general of the usual construction, and since the various elements to which reference has been made are commonly found in one form or another in all modern open hearth steel furnaces, further reference thereto or detailed description thereof would be superfluous.

Under usual conditions of furnace operation, the greatest erosion of the roof takes place adjacent the front and back walls, and it is therefore desirable that the roof in this vicinity be made of sufficient thickness to adequately resist the destructive effects of the hot gases and permit a certain amount of material to spall off without undue weakening of the roof structure as a whole. However, I have found that when the roof is made the same thickness throughout, the weight thereof adjacent the center is such that when the roof ultimately becomes weakened adjacent one of the side walls through the erosion of the gases, it tends to buckle in the vicinity of the weakened spot and finally to collapse inwardly into the hearth, this effect being especially noticeable if a hole is burned through the roof near one of the side walls.

To obviate this condition, I construct the roof of normal thickness adjacent the side walls, carrying this thickness oppositely inwardly for any suitable distance, for example, about one-fourtli of the total roof span on each side using for this purpose refractory bricks A of any suit-able composition and desirably of standard size for structures of this character, and then make the remainder of the roof, and thus adjacent the center, of considerably less thickness as best shown in Fig. 2. The bricks B which form this section being composed of the same material but desirably of smaller dimensions and so arranged in the roof that their upper surfaces complete the curve of the upper surface of the side sect-ions, the differences in the thicknesses of the bricks thus resulting in the formation of abrupt, radially extending shoulders between the side and central sections. Thus, for example, the bricks A which forln the side sections may be 12 long, their end faces being exposed, and the central section bricks B are then desirably 9 long and are also laid with their end faces showing. This area of reduced thickness may be provided merelyf above the hearth or may be carried up into the throats of the furnace at each end as may be desired. In this manner I am able to diminish the weight of the roof as a whole and to reduce the amount of material initially required therefor, while because of the fact that the center part of the roof is relatively light, the thrust exerted thereby against the side portions is correspondingly lessened; in consequence, if the roof is weakened or burned through near either side bythe gases in the hearth, there is distinctly less tendency for the roof to collapse as a whole than in the case of a roof of usual construction which is of uniform cross sectional thickness throughout its ext-ent.

It will, of course, be understood that the principles of my invention may be employed in furnaces of other types than that to which I have chosen to refer and that variations in the design, construction and arrangement of the different parts may be made, if desired, without departing from the spirit and scope of the invention as defined in the appended claims.

Having thus described my invention, I

claim and desire to protect by Letters Patent of the United States:

' l. In an open hearth furnace having a hearth andfront and back walls, a roof extending transversely over the hearth from one of said walls to the other and having a sharply defined zone adjacent its center extending longitudinally of the furnace of less thickness than the Zones lying on each side of said first mentioned zone and extending to said walls, the inner surface of said sharply defined central zone, being radially outwardly offset from corresponding sui'- faces of the Zones lying on either side thereof.

2. In an open hearth furnace having a hearth and front and back walls, a refrac- .tory roof extending above the hearth and supported from said walls, said roof having a plurality of coaxial sections of transversely arcuate contour extending longitudinally of the furnace and respectively of uniform radial thickness, the front and back sections being substantially congruent and the central section being radially outwardly offset therefrom and formed of refractory brick of less radial thickness than the bricks forming the front and back sections.

3. In an open hearth furnace having a hearth and front and back walls, a roof extending above the hearth and supported from said walls, said roof having arcuate side sections extending longitudinally of and respectively adjacent said walls and formed of refractory bricks of uniform radial thickness, and an arcuate central section coaxial with and interposed between said side sections and oining the respective uppermost extremities thereof, said central section bcing formed of refractory bricks of lesser thickness than those forming the side sections and having their lower faces radially offset from the corresponding faces of the bricks of the side sections whereby a radially extending shoulder is formed internally of the furnace at the junctions of the side and central sections.

In witness whereof, I have hereunto set my hand this 15 day of December, 1930.

ELMER E. MGVEY.

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